In another application filed concurrently herewith by the present inventor and Yasutada Yuza, applicants described a so-called chip-type fuse (or chip fuse) which does not require lead wires or fuseholders. These chip fuses are extremely miniaturized and especially adapted for use in a printed circuit board (PCB) and, as disclosed in said application, these fuses comprise electrically conductive terminals which have a portion exposed outside the fuse base adapted to be soldered to the PCB. Where overheating of the PCB is not a serious problem, such chip type fuses are satisfactory. In some instances, however, overheating of the PCB could be problematic. This is particularly true when using highly dense electronic circuits which comprise many heat-generating components, such as resistors and transistors which are cramped into a very limited space on the PCB. Frequently in such circuits, the temperature of the PCB could rise to as high as 60.degree. to 70.degree. C. due to the heat generated by the aforementioned components. Thus, if the fuse base is mounted directly on the PCB, the heat generated in the PCB could adversely affect the function of the fuse since the fusible element may melt prematurely at a current which is lower than the rated current of the fuse. In addition, the fuse may deteriorate due to repeated usage over the years.
Another consideration in a chip-type fuse is the optimum amount of solder which is used to solder the conductive terminals to the PCB. If excessive amount of solder is used, the heat capacity of the terminals may vary widely, thus causing dispersion of the blowing time of the fusible element.
Additionally, if the fuse cover is adhesively bonded to the fuse base, the heat generated during soldering may melt the adhesive or destroy its bonding strength. Consequently, some water vapor or other harmful gases may penetrate the fuse base and cause corrosion of the fusible element.
Accordingly, it is an object of the present invention to provide a chip-type fuse which eliminates, or at least minimizes, the aforementioned disadvantages.
It is a further object of this invention to provide a chip-type fuse which does not require lead wires or a fuse-holder when used in a PCB.
The foregoing and other objects, features and advantages of the present invention will be appreciated from the following detailed description and the accompanying drawings.